There's an oft repeated story from one of the game developers about Clint's involvement. Pasted below:

The game was in development during the time Clint was
shooting/directing/editing/etc. Bridges of Madison County. After
contacting his people about getting him to record custom speech for the
game, we were generally told that he was too busy, but a sound-alike
would be just fine. So we brought in our standard sound-alike guy who
did a GREAT job. His Dirty Harry voice was everything you could want in
a Dirty Harry pinball game; growly, angry, exciting, big than life, etc.
Generally, exactly waht you REMEMBER Harry to be in the movies (which
isn't necessarily what he WAS in the movies).

Pretty close to the end of the development cycle, Clint's people called
and said that now he WOULD have time to do the speech, since he was
doing some dialog replacement stuff at a sound studio. So Vince, the
sound guy, flew out and did a recording session with Clint.

Well, Vince comes back, and we're naturally all excited to hear his
stuff. And we were all pretty disappointed, with what I'd call, at best,
a very Disinterested Harry. Now given the situation, I don't think
anyone can be blamed, as there were many factors involved here:
a) Clint had a lot of things on his mind at the time, and pretty much
only had a hour to spare to read a very long set of dialog.
b) Clint at the time was now over 20 years older than when he was when
he filmed the first movie, and pretty much acnowledged that to Vince.
"It's been a long time since I've played this character."
c) It's gotta be very intimidating to have Clint in the sound booth and
try directing him "C'mon Clint, grit your teeth a little bit more, sound
ANGRIER!! Trust me, I know how your classic character should sound."
d) And just the fact that we REALLY liked the way the sound-a-like
turned out.

Unfortunately, everyone felt compelled that we had to use Clint's speech
even though we weren't very happy with it. So, rest assured that every
speech call in the game was specially recorded for the game. And when
Dirty Harry leans back and finishes his coffee as he off-handedly
mutters "Hey, that punk just stole my car" in a voice that seems to want
to add "but that's okay, it's a rental," you can be sure that it's Clint
Eastwood.